I was suspicious of it too! The growl started inside the converter when I
placed a mix 31 ferrite on the DC line. I immediately removed the ferrite
core.The ferrite core on the DC line indeed caused the growl to become audible
from the converter.The growl from the converter when the ferrite was in place
on the DC line was disconcerting enough that I didn't take time to check if it
reduced the spurious HF output.The core was only on the positive line, so not
in common mode.I have a mix 31 core that's about 4 in in diameter. I could
probably get a couple of turns of both the positive and negative DC lines
through it, if that warranted a try. Go with a CM choke.The mix 31 I placed on
the AC line at the input of the converter was common mode. But as noted in my
initial post, it had no effect whatsoever. Nor did an isobar power strip with
its filtering components.I also did try a large value electrolytic (87,000
microfarad) across the DC line, but no effect.Smaller value capacitors across
the DC line likewise made no change.Jim has me wondering if focus on the DC
line with a common mode choke holds promise. The growl from the converter with
the choke only on the positive lead made me abandoned that, pronto. Perhaps
prematurely.Per WA2LBI's suggestion I also have an inquiry in with Iota
regarding their converters.Thanks to everyone who's responded. It is very much
appreciated. ScottSent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Jim Brown <jim@audiosystemsgroup.com>
Date: 7/22/22 14:53 (GMT-05:00) To: rfi@contesting.com Subject: Re: [RFI]
Travel trailer converter RFI solutions On 7/22/2022 11:42 AM,
k1ttt.dave@gmail.com wrote:> I would be very suspicious of the growl caused by
ferrites on the dc line,Dave,That "growl" (great description) is harmonics of
rectangular waves produced by switched-mode power supplies and power control
electronics like the controllers for variable speed motors. Growl is not CAUSED
by ferrites, SUITABLE ferrite chokes can SUPPRESS it on circuits that carry
those currents. The 2-wire transmitting chokes in this link are also suitable
in this application. http://k9yc.com/2018Cookbook.pdf73, Jim
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